Dual-diaphragm microphone module to reduce vibration noise

Abstract

A microphone module disposed in an electronic device for reducing echo noise. The microphone module includes a casing, a first diaphragm disposed in the casing, a second diaphragm disposed in the casing and a substrate disposed between the first diaphragm and the second diaphragm and joined to the casing to define a first space and a second space which are isolated and separated from each other. The first diaphragm is disposed in the first space, the second diaphragm is disposed in the second space, and the substrate is electrically connected with the first diaphragm and the second diaphragm.

What is claimed is: 
     
       1. A microphone module, comprising:
 a casing; 
 a first diaphragm disposed in the casing; 
 a second diaphragm disposed in the casing; and 
 a substrate disposed between the first diaphragm and the second diaphragm and joined to the casing to define a first space and a second space which are isolated and separated from each other, 
 wherein the first diaphragm is disposed in the first space, the second diaphragm is disposed in the second space, and the substrate is electrically connected with the first diaphragm and the second diaphragm, 
 wherein the casing includes an air hole, the first diaphragm is exposed to the air hole and is directly opposite thereto, and the second diaphragm is not exposed to the air hole such that only the first diaphragm is influenced by an external audio signal. 
 
     
     
       2. The microphone module of  claim 1 , wherein the microphone module is mounted on a chassis. 
     
     
       3. The microphone module of  claim 2 , wherein the first diaphragm is vibrated as a result of a sound signal passing through the air hole and as a result of vibration of the chassis. 
     
     
       4. The microphone module of  claim 2 , wherein the second diaphragm is vibrated only as a result of vibration of the chassis. 
     
     
       5. The microphone module of  claim 2 , wherein the first diaphragm and the second diaphragm are arranged such that the first diaphragm and the second diaphragm vibrate in opposite phases with respect to each other when the chassis vibrates. 
     
     
       6. The microphone module of  claim 1 , in combination with an electronic device that comprises an echo cancellation circuit. 
     
     
       7. The microphone module of  claim 6 , wherein the echo cancellation circuit is configured to operate to eliminate substantially only on an external audio signal generated by a speaker of the electronic device. 
     
     
       8. The microphone module of  claim 6 , wherein the electronic device is one of a smart phone, an e-book, or a computer. 
     
     
       9. A method for operating an electronic device, the electronic device comprising a speaker and a microphone module both mounted on a chassis of the electronic device, the method comprising:
 driving the speaker with a first electric signal representative of an audible audio signal; 
 detecting, at the microphone module, an internal audio signal component and an external audio signal component of the audible audio signal, the internal audio signal component resulting from vibration of the chassis of the electronic device; and 
 reducing an electric signal representative of the internal audio signal component by combining outputs of a pair of oppositely disposed diaphragms in the microphone module, 
 wherein a first diaphragm of the microphone is disposed in a first space and is directly opposite an air hole, a second diaphragm is disposed in a second space isolated from the first space and without an air hole, the first and second diaphragms being oppositely disposed, and 
 wherein only the first diaphragm is influenced by the external audio signal through an air hole. 
 
     
     
       10. The method of  claim 9 , wherein detecting comprises detecting the internal audio signal component with the first and second diaphragms. 
     
     
       11. The method of  claim 9 , further comprising outputting, from the microphone module, a second electric signal representative of the external audio signal component detected in the step of detecting. 
     
     
       12. The method of  claim 11 , further comprising reducing the external audio signal component by combining the second electric signal with a third electric signal that is a processed version of the first electric signal. 
     
     
       13. The method of  claim 11 , further comprising generating the third electric signal by at least one of attenuating, delaying or phase shifting the first electric signal.